Conventionally, various types of techniques have been proposed by which a heart surgery treatment is aided by taking an image of the inside of the body of the examined subject (hereinafter, “patient”). For example, among various treatments of mitral valve closing insufficiency is a treatment by which the volume of regurgitation is reduced by inserting a catheter to the mitral valve of the heart through a blood vessel in a thigh (a femoral vein) and holding the mitral valve with a clip-shaped tool. For such a treatment, for example, a technique has been proposed by which the position of the tool (the catheter) inserted toward the mitral valve is accurately displayed by using an X-ray fluoroscopic image and a Transesophageal Echocardiography (TEE) image taken during the surgical operation. Further, for example, another technique has also been proposed by which an image for guiding an advancing course of the catheter is displayed by aligning the position of a Computed Tomography (CT) image taken prior to the surgical operation with the position of an image taken during the surgical operation.
Further, techniques have been proposed by which the field of vision is varied so as to follow movements of a puncture needle.